Purpose: :
It has been speculated that NITM (accommodatively-based nearwork-inducedtransient myopia) is myopigenic in nature. Thus, the purposeof the present investigation was to determine objectively theinitial magnitude of NITM, and its potential additivity, followingsuccessive but interrupted periods of marked, sustained accommodationat near in asymptomatic young adult myopic subjects.

Methods: :
Fifteen visually normal, asymptomatic young adults (ages 18- 28 years) were tested with full distance refractive correction.They included 9 early-onset (EOM) and 6 late-onset (LOM) myopicsubjects. Accommodation was assessed objectively with a CanonR-1, open-field infrared auto-refractor under monocular viewingconditions (RE). The distance refractive state was measuredimmediately before and after each of the 3 ten minute periodsof focusing upon a moderate contrast (50%), near target (12cm; 8D) subtending 6 degrees. The task was repeated twice witha 5-minute inter-task rest period of imposed far viewing. NITMwas defined as the post-task minus pre-task change in distancerefractive state immediately following each task.

Results: :
Significant amounts of NITM were generated following each trial.These ranged from 0.11 to 0.71D, with a mean of 0.31D. The groupmean NITM was 0.32, 0.29, and 0.31D for trials 1, 2, and 3,respectively. For the EOMs subgroup, NITM was 0.28, 0.30, and0.34D, while for the LOMs subgroup, it was 0.38, 0.29, and 0.26D,for for trials 1, 2, and 3, respectively. However, additivityof NITM was not found following the sequence of interruptednear tasks.

Conclusions: :
There was no evidence of NITM additivity following a markedand sustained, but interrupted, near task. Although NITM hasbeen reported to be additive following long periods of sustainedreading (Vasudevan & Ciuffreda, 2008), providing rest periodsbetween near task trials appears to prevent a cumulative effect.These findings support the idea of far viewing being protectivein nature from myopia development.